Homoplasty

Homoplasty, or homoioplasty (from Greek homoios - similar), isoplasty, free transplantation of tissues or organs from one individual to another of the same species, including from one person to another. The beginning of successful transplantations in surgery coincides with the introduction of the aseptic method, as suppuration of wounds until that period usually doomed any transplantation to failure. At first, surgeons did not even consider that there might be any difference in the take of a flap taken from the patient himself or from another person. Since in the 1870-1880s transplantation of skin according to the Reverdin method was mainly performed and sometimes very many small flaps were required, they often resorted to borrowing these flaps from other people, mainly relatives. These foreign flaps were mixed with the patient's own flaps; of course, not all took, and in evaluating the final result, little attention was paid to which specific flaps took and which died - the patient's own or foreign ones. But in cases where exclusively foreign skin was used, i.e., when homoplasty was performed, it was soon noticed that in these cases failure usually occurred; the transplanted flaps either immediately died and were rejected or, after an initial apparent take, gradually but quite quickly - on the 2nd-3rd-4th week - seemed to melt away and resorb. The actual fate of free grafts became clear only when, to clarify this question, microscopic examination of transplanted tissues was used in experiments on animals immediately after transplantation (Machand). In this way, it was revealed that much of what was considered capable of taking actually did not take, but died and was replaced through regeneration. This method of study had a particularly strong impact on the evaluation of the fate of homoplastic transplantations. It was precisely in such transplantations that the clinical success observed in some cases was due to regeneration of the host tissues, not the actual take of the graft. Homoplastic transplantations succeed well in lower animals (hydroids, planarians, echinoderms, worms). Jost, who studied transplantations on earthworms, does not even find it necessary to note the difference between auto- and homotransplantations. But the results are quite different in vertebrates. Even in frogs, homoplastic skin transplantations almost never give true take; at best, a small part of the transplanted flap takes. Embryonic tissues are more capable of such take, even when transplanted to adult animals. In Fig. 2 (see separate table, pp. 215-216), one can see how a limb bud of a toad, transplanted to an adult animal, not only took but also grew into a complete limb. The same is sometimes observed in higher animals. In Fig. 3 (see separate table, pp. 215-216), a mouse is shown on whose back skin from its newborn, still hairless, offspring was transplanted. This skin took, became covered with hair, and ears grew on it, which the newborn did not yet have. Besides the age of the graft, the relationship between donor and recipient also plays a role: transplantations from young offspring to parents work best. In humans, as mentioned above, homoplastic transplantations have been performed since ancient times, but the results have always been poor. And if one takes into account that good clinical results can be obtained even with the complete death of the graft due to regeneration of adjacent tissues, it will become clear how rarely homografts actually take. Different tissues react differently to such transplantations. Connective tissue and its derivatives - fibrous connective tissue, tendons, fasciae, adipose tissue, cartilage, partly bone, more precisely the periosteum - are capable of homotransplantation, although histological examination of the fate of such grafts shows that the partial degeneration of the graft observed in autotransplantation is much more pronounced here: less of the flap remains, it is more overgrown with connective tissue from the outside, it shrivels. The percentage of complete failures is also higher. As for epithelial organs, they give even worse results, so practically one can speak of the impossibility of such transplantations under homoplastic conditions. In some cases, homoplastic transplantation of cornea succeeds (up to 10%). Endocrine glands, capable of autotransplantation, almost always die in homoplasty, although individual cases of true take are still observed. Only the microscope, not the clinical result, determines the true fate of the graft. (Transplantation of individual organs - see respective organs.) As for the reasons for the poor success of homoplasty, only general assumptions can be made. It is quite certain that the tissues and fluids of different people differ from each other in their physical, chemical, and biological properties. The concentration of hydrogen ions, the amount of Ca, Mg, K, sugar, cholesterol, etc. show significant fluctuations and can be quantitatively determined. Purely biological reactions, such as hemolysis, agglutination, etc., indicate deeper biological differences. More differences cannot yet be noted by us. However, what has been said is sufficient to understand that the nutritional conditions for the graft in its new location may prove unsuitable for it. Experience shows that the tissues of two individuals of the same species can not only be unsuitable but actually poisonous to each other. Schone killed white mice by injecting emulsions of organs and tissues of another white mouse in an amount of only 0.5 g. Since blood transfusion is nothing other than homoplastic transplantation of the liquid tissue blood and gives a positive result only in people of the same blood groups, it naturally suggests itself to assume that homoplasty will also be possible between individuals of the same group. Few observations in humans have so far not confirmed this assumption, while experiments on animals are impossible because blood groupings have not yet been established in animals. To smooth the biochemical differences between the host and the graft, attempts were made to pre-soak the latter in the blood of the future host: the results were significantly better but not perfect - the grafts died, but only after much longer periods. To prevent the formation of antibodies, the site of production of which is now considered to be the reticulo-endothelial apparatus, Tamman and Lehmann simultaneously blocked the reticulo-endothelial system with trypan blue when transplanting skin from one white mouse to another; the skin flaps took and remained as long as the blockade continued; when the blockade was stopped, the flaps resorbed quite quickly. Preliminary preparation of both donor and recipient by cross injections of blood only worsened the results, apparently preparing the formation of protective bodies; perhaps one needs to guess the amount of blood or serum to be injected. In the final analysis, it must be said that artificial methods have so far succeeded very little in improving the results of homoplasty. Therefore, in practical surgery, where possible, autotransplantations should be preferred to homoplastic ones. The latter can only be done 1) in transplantation of connective tissue and cartilage, capable of homoplastic take; 2) in transplantation of bone into bone defects, counting on bone regeneration. The same applies to tendon transplantation. All this on the condition that obtaining autotransplantation material presents great difficulties. The combination of partial take with regeneration can give brilliant results in some cases. In Fig. 4 and 5 (see separate table, pp. 215-216), a patient is shown whom Lexer transplanted, after resection of the knee joint, a joint taken from a just amputated limb. The photograph was taken 2 years 5 months after transplantation and shows excellent joint function. 3) In transplantation of endocrine glands, since these transplantations are always performed with insufficiency of the patient's own glands and therefore autotransplantation is excluded.